On Fri, May 21, 2021 at 02:41:56PM -0500, Madhavan T. Venkataraman wrote:

quoted

Or is frame->reliable supposed to be checked after all?  Looking at the
code again, I'm not sure.

Either way it would be good to document the interface more clearly in a
comment above the function.

So, arch_stack_walk_reliable() would do this:

	start_backtrace(frame);

	while (...) {
		if (!frame->reliable)
			return error;

		consume_entry(...);

		ret = unwind_frame(...);

		if (ret)
			break;
	}

	if (ret == -ENOENT)
		return success;
	return error;


Something like that.

I see.  So basically there are six possible combinations of return
states:

  1) No error		frame->reliable
  2) No error		!frame->reliable
  3) -ENOENT		frame->reliable
  5) -ENOENT		!frame->reliable (doesn't happen in practice)
  4) Other error	frame->reliable  (doesn't happen in practice)
  6) Other error	!frame->reliable


On x86 we have fewer combinations:

  1) No error		state->error
  2) No error		!state->error
  3) Error		state->error
  4) Error		!state->error (doesn't happen in practice)


I think the x86 interface seems more robust, because it's more narrow
and has fewer edge cases.  Also it doesn't have to distinguish between
error enums, which can get hairy if a downstream callee happens to
return -ENOENT for a different reason.

-- 
Josh